The subject matter of the present application is related to subject matter disclosed in U.S. patent application Ser. No. 08/487,117, entitled xe2x80x9cComputer System with Displayxe2x80x9d, in application Ser. No. 08/485,876, entitled xe2x80x9cDisplay FIFO Module including a Mechanism for Issuing and Removing Requests for DRAM Accessxe2x80x9d, and in U.S. patent application Ser. No. 08/486,796, entitled, xe2x80x9cComputer System with Double Simultaneous Displays Showing Differing Display Imagesxe2x80x9d, all filed on the same day and assigned to the assignee of the present application.
1. Field of the Invention
The present invention relates generally to a computer system with a display device, such as a cathode ray tube (CRT) or liquid crystal display (LCD), for example. The display device provides a user of the computer system with a visible display of computer data, such as test or graphics. More particularly, the present invention is in the field of such a computer system having a Video Display Controller (VDC) including a graphics generator. The VDC receives image information, such as text or graphics generated by a processor (CPU) or retrieved by the CPU from another facility (such as a CD-ROM) of the computer system, and provides signals driving the CRT or LCD display. The computer system may be a battery-powered portable device. Still more particularly, the present invention is in the field of a VDC having a power saving mode for responding to both hardware inputs (such as a contact closure input, for example) and also to a software input to effect a reduction in power consumption within the VDC and the computer system as a whole.
2. Related Technology
A conventional power manager for a portable laptop computer is known in accord with U.S. Pat. No. 5,167,024 (hereinafter, the ""024 patent), issued 24 Nov. 1992 to R. Steven Smith, et. al. According to the ""024 patent, a power manager for a laptop computer provides power management and clocking control to various units of the computer. Switches control the distribution of power to the various units of the computer. When any of these various units are not needed, the switches are used to remove power or clock signals, or both, from particular units of the computer. The power manager allows the computer to be in any one of four states varying from xe2x80x9conxe2x80x9d and active, to xe2x80x9conxe2x80x9d in a xe2x80x9csleepxe2x80x9d state with power and/or clock signals removed from certain units, to xe2x80x9conxe2x80x9d in an xe2x80x9cintermediatexe2x80x9d or xe2x80x9cslowxe2x80x9d state in which the clock rate of the computer is reduced to result in a power saving. The fourth state for the computer system is xe2x80x9coffxe2x80x9d.
With a power manager as disclosed in the ""024 patent, a system designer is limited to three functional modes for the computer, only two of which are modes with reduced power consumption. Further, the system criteria which will initiate one of the two modes of reduced power consumption are relatively limited.
Another conventional real-time power conservation apparatus for portable computers in known in accord with U.S. Pat. No. 5,218,704 (hereinafter, the ""704 patent), issued Jun. 8, 1993 to LaVaughn F. Watts, Jr., et. al. According to the ""704 patent, a real-time power conservation apparatus for a portable computer employs a monitor to determine whether a computer may rest based upon CPU activity. A hardware device carries out the result of the monitor""s determination. Again, with this conventional power conservation apparatus, the system designer options as to how power conservation expedients are to be implemented are limited.
Yet another conventional power management system for a battery-operated, computer is known in accord with U.S. Pat. No. 5,230,074 (hereinafter, the ""704 patent), issued Jul. 20, 1993, to Francis J Canova, Jr., et.al. According to the ""074 patent, a battery-operated computer includes two processors, a main processor, and a processor which manages power receipt (battery charging) and power usage within the computer. The system designer using the power management system taught by the ""074 patent would be constrained to configure the power management options of a computer system according to the choices allowed by the teaching of this patent.
Two more recent conventional power saving or power conservation apparatus are known in accord with U.S. Pat. Nos. 5,369,711; and 5,396,635, issued 29 Nov. 1994, and 7 Mar. 1995, respectively, to Steven J. Gettel, and Henry T. Fung, also respectively. These teachings both employ software routines to control a monitor for determining which of available power conservation or power saving expedients are to be implemented. A user of either one of these power saving expedients will be required to select from among a limited field of power saving configurations for each mode of operation of the computer system. Also, implementation of these power saving apparatus is rather complex, requiring use of separate power management IC.
Accordingly, a long-felt need has been recognized in the field of battery-operated portable computers for such a computer system which has both a high level of graphics generating capabilities and an economy of operation effected by a power saving facility of the VDC of the computer system which results in a comparatively long battery-powered service life between battery recharging.
In view of the deficiencies of the conventional technology, an object for this invention is to provide a computer system with a video display controller avoiding one or more of these deficiencies.
Another object for this invention is to provide such a computer system with a video display controller (VDC) receiving image information, such as text or graphics, and providing signals driving a display.
Yet more particularly, the present invention has as an object the provision of a portable batter-powered computer system with a VDC having its own power saving facility.
Still more particularly, the present invention has as an object the provision of such a VDC for a portable battery-operated computer system which provides a system designer with a variety of optional power saving modes which may individually be configured as the system designer wishes, and which are implemented individually or sequentially, dependent upon system operation parameters and user conduct.
Accordingly, the present invention provides a computer system including an input device for receiving inputs from a user; a central processing unit (CPU) interfacing with the input device and responding to the inputs by performing a processing function producing an output; an output device receiving the output response from the CPU and providing a sensible output response; the output device including a display device providing a visible image to the user in response to the output response; a video display controller (VDC) interfacing with the CPU and providing driving signals to the display device, the VDC including a power saving controller, the power saving controller including a register providing a plurality of power saving modes, each power saving mode including a plurality of functions of the VDC each of which are individually enabled or disabled when the respective power saving mode is activated dependent upon a bit value entered into a respective location on the register.
As a result, a system designer can configure a computer system using the present VDC as is desired to implement a variety of differing power saving modes, dependent for example, on the selection of components included in the computer system. Each of the available power saving modes allows the system designer a complete choice of which functions of the computer are to remain enabled and which are to be turned off or modified in response to activation of each power saving mode. Virtually the only restraint imposed on the system designer is the order of succession of the various modes. The power saving modes are ranked in succession, and when a higher ranking mode is activated the lower ranked modes of power saving are succeeded. Additional objects and advantages of the present invention will be apparent from a reading of the following detailed description of particular preferred embodiments of the present invention, taken in conjunction with the appended drawing Figures, in which like reference numeral indicate the same feature, or features which are analogous in structure or function.